<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
    function fn(a,b)
    {
        console.log(a+b);
    }
    fn(1,2);
    fn(5);
    fn(4,6,9);
    
</script>
</body>
</html>